Highly Dispersive Palladium Loading on ZnO by Galvanic Replacements with Improved Methane Sensing Performance

Methane detection is important for the safety of production and life. Metal oxide semiconductor (MOS) methane detection is a mature and widely used technology but still experiences problems such as unsatisfying low-temperature sensing performances. In this study, ZnO/Pd with Pd nanoparticles of different diameters was prepared to study the influence of Pd dispersion on CH4 sensing properties. Results showed that CH4 sensing enhancements were positively correlated with the dispersity of Pd. Moreover, by galvanic replacement using Ag as the sacrificial template, a highly dispersive loading of Pd on ZnO was realized, and the CH4 sensing performance was further enhanced while the amount of Pd reduced from 1.35 wt% to 0.26 wt%. Experiments and DFT calculation indicated that improved CH4 sensing performance resulted from abundant catalytic sites induced by highly dispersed Pd NPs and the enhanced CH4 adsorption on positively charged Pds caused by electrons transferred from Pd to Ag. This study provides a strategy to achieve high dispersion of Pd to maximize the utilization of noble metal, which is promising for lowering the cost of the MOS-based CH4 sensors.